Variable escapement



R. A. GREA EI'AL VARIABLE ESCAPEMEINT Match 5, 1957 3 Sheets-Sheet 1 3 59 l 9 2 l .l m. A d e l i P.

Fig.2

INVENTORS RENE A. GREA RENE A. HIGONNET LOUIS M. MOYROUD 1 g umzi:v Ylx/L/ ATTORNEYS Filed April 29, 195;

INVENTORS GREA RENE A; HIGONNET LOUIS M. MOYROUD RENE ATTORNEYS R. A.GREA E'l'AL VARIABLE ESCAPEMENT March 5, 1957 Filed April 29; 1953 3Sheets-Sheet 3 ATTORNEYS.

United States Patent'O VARIABLE ESCAPEMENT Rene A. Grea and Rene A.Higonnet, Cambridge, and Louis M. Moyroud, West Medford, Mass.,assignors to Graphic Arts Research Foundation, Inc., Cambridge, Mass, acorporation of Delaware Application April 29, 1953, Serial No. 351,824

1 Claim. (Cl. 74-1.5)

The present invention relates to variable advance mechanisms such as aresuitable for displacing photographic film in photographic type composingmachines of the kind described in the copending applications of Higonnetand Moyroud, Serial Nos. 610,336 and 770,320 filed August 11, 1945, andAugust 23, 1947, respectively.

The principal object of the present invention is to provide a variableescapement mechanism by which the extent of desired movement may berapidly selected and the movement may be effected with exceptionallyhigh precision. With this object in view, the invention comprises thevariable escapement mechanism hereinafter described and particularlydefined in the claims. The apparatus of. the present invention isparticularly suitable for use with composing apparatus of the typedescribed in the above-mentioned applications, because of the precisionrequired in such apparatus.

The invention will be particularly described with reference to apreferred embodiment in which Fig. 1 is a sectional elevation of thedrive for the film carriage;

Fig. 2 is an elevation of the film carriage;

Figs. 3 to 7 are sectional elevations of the escapement, being takengenerally on line 33 of Fig. 8;

Fig. 8 is a section on line 8-8 of Fig. 3; and

Fig. 9 is a view similar to Fig. illustrating a modification of theescapement.

Referring to Figs. 1 and 2, the sensitized film passing from a feedmagazine to a take-up machine (not shown) is supported and fed by asprocket 1F, a presser 3F, and a take-up sprocket 2F. Motions of thesprocket are used to advance the film for spacing between lines.

The lateral movement of the film during the photographing of a line iseffected by a transverse movement of the carriage, controlled by a screwof relatively low pitch 17F (not reversible) which rotates under thecontrol of a variable escapement to be described in detail presently.The escapement includes a gear wheel 37F which rotates, after eachphotographic exposure, through an angle corresponding to the width ofthe particular character photographed. This wheel meshes with a pinion19F which itself meshes with a pinion 20F pinnedon shaft 29F, whichshaft carries the screw 17F. Conical roller bearings 21F and 22F areprovided for the shaft 29F, and the rotary movement is transmitted tothe film carriage in the direction of arrow F (Fig. 1).

The displacement of the carriage must be effected with utmost precision,of the order of .0005 of an inch. In

order to reach this high degree of precision it is neces-,

sary to take up any backlash which may be present. This is accomplishedby means of two springs which are also used for bringing the filmcarriage back to its rest position after the line has been photographed.One of these springs drives a wheel 23F (Fig. 2) and pulls the filmcarriage by means of a wire 24F in the direction of a return movement ofthe carriage. The other spring acts on screw 17F by means of a coiledwire 25F and tends to rotate this screw in the reverse direction.

Each time a character has been photographed, the film carriage is movedto the left a variable distance in a relatively short time. In order toobtain the required precision it is necessary to absorb the greater partof the shock due to stopping the carriage. To this effect a flexiblearrangement has been provided, comprising a ring 26F which slides on theframe of the machine and presses against the conical bearing 22F. Thisring is held in position by a powerful spring 27F whose tensionmay beadjusted by member 28F screwed into the frame. After each movement ofthe carriage, wheel 37F stops suddenly, and due to inertia, the carriagehas a tendency to continue its movement. Owing to the pitch of thescrew, a component of force would be applied in a rotative direction tothe shaft 29F and this would result in a shock applied to the teeth ofthe wheel 37F. The effects of shocks thus applied to the wheel 37F andother parts of the escapement would be to affect their precision.According to the described arrangement, however, the longitudinalinertial force is applied to the thrust bearing 22F by a shoulder 30F ofshaft 29F, and is transmitted to ring 26F which moves very slightly andcompresses spring 27F. The spring then re-expands and restores the partsto exact position. The energy due to motion of the carriage isdissipated in friction, and there is no appreciable component of forcethat is transmitted to the gears of the escapement.

When one line has been completely photographed, electromagnet DEB isexcited. This magnet pulls plunger 32F against spring 31F, and drivespinion 19F which slides on a rod 33F mounted on the frame of themachine. This pinion disengages itself from wheel 37F while remainingmeshed with pinion 20F. As soon as pinion 19F is disengaged from wheel37F, the springs acting on wire 25F and wheel 23F cause screw 17F torotate in the direction opposed to its normal course of rotation, andbring the film carriage quickly back to its initial position forphotographing the following line. Suitable mechanism may be provided forsetting the carriage in a precise initial position, but such mechanismis described in'application Ser. No. 770,320 and forms no part of thepresent invention.

Under normal operating conditions pinion 19F is held meshed with wheel37F which slides freely in a fixed member 35F and is constantly pushedby an adjustable spring 31F.

The variable escapement mechanism, which controls the advance of thefilm carriage, will now be described with reference to Figs. 3 to 9.

This variable escapement comprises the gear 37F meshing with the pinion19F which controls the rotation of screw 17F of the film carriage, asabove described. This gear rotates through a number of teeth, dependingon the width of the carriage which has just been photographed, and it isunder the control of a star niece 38F having several arms whosedisplacement is limited by pins or abutments 41F equal -in number to thedifferent possible advances. A toothed sector 39F on the star piece 38Fcan mesh'with a pinion 40F. In the preferred embodiment, the pins 41F,as shown in Fig. 8, are arrangedso that normally they lie beyond thepath of movement of any of the arms of the star piece, but any one pinmay be pushed into position to beengaged by one of the arms.- Preferablyeach pin is under the control of an individual electromagnet. Except forthe difficulty of placing all the pins and magnets in a suflicientlysmall space, one arm would sufiice for the star piece. By the use ofseveral arms it is possible to arrange the pins so that one selected pinwill lie in the path of an arm in a way to give a precise predeterminedamount of angular motionof the wheel.

The mechanism for selecting a particular pin is not shown, since itforms no part of the present invention.

Patented Mar. 5, 1957 areas r After a particular pin (41F) is selected,the motor electromagnet 42F (Fig. 3) is then excited and pulls controlrod 43F. This control rod is provided with two shoulders 44F and 45F andslides through an opening provided in the tail 46F of a pawl lever 47F.This lever pivots about a shaft 48F. When rod 43 begins to move, spring49F pushes lever 47F and holds it against the stop member 44F. The pawlmeshes with gear 37F, thus holding it stationary.

Rod 43F continues its travel. Its shoulder 50F pushes the end of a lever51F bearing a pinion 40F. This lever turns about its shaft 52F and freespinion 40F from gear 37F. Pinion 40F meshes then with an abutment member53F which holds it in position.

At the same time, star piece 38F, whose toothed sector 39F was meshedwith pinion 40F, is also freed and moves counter-clockwise under theimpulse of a prewound spring (not shown),until one of its arms meetsstop pin 41F (Fig. At this moment rod 43F has finished its travel, andthe shoulder 45F holds pawl 47F in mesh with gear 37F. A pawl 54F, whichis normally held in engagement with the teeth of gear 37F by spring 55F,falls back into engagement with the gear 37F and prevents any possiblebouncing back of the star piece 38F.

The mechanism remains in this position until the electromagnet 42F isreleased. At this moment rod 43F is returned by the action of spring 61F(Fig. 6). In the first part of this backward movement, the end 62F ofshoulder 50F meets the end 63F of lever 51F and this lever rocks. Pinion40F on lever 51F meshes at the same time with the gear 37F and with thetoothed sector 39F of the star piece. Part 62F slides under part 63F andholds pinion 40F in position.

Near the end of its return motion, rod 43F frees pawl 47F from gear 37F(Fig. 7). At this moment the gear, urged by a pre-wound mam spring (notshown), rotates clockwise and drives the star piece 38F until the part57F comes against a stop member 64F. Gear 37F and star piece 38F movesimultaneously, since they are both in mesh with pinion 40F. Thus inthis motion, the Wheel 37F measures off a precise angular motiondetermined by the position of the selected pin 41F in relation to thestop 64.

In order to take up the shock of stopping the parts, a damper 56F isprovided. It comprises a member, which in the position of Fig. 3, ispushed back by the end 57F of the star piece 38F against the tension ofa spring 59F. The damper is pivoted at 58F. The damper has aconsiderable mass. When the star piece leaves the stop 64F for itscounter-clockwise movement (Fig. 5) the damper turns into engagementwith, an abutment 60F. On the clockwise motion of the star piece, thedamper swings through position 56'F to 56"F (Fig. 7) back to itsposition of Fig. 3. The kinetic energy of the moving parts is dissipatedin the damper.

Fig. 9 illustrates a modification of the variable escapement whichpermits the number of different movements that may be achieved by usinga given number of pins 41F to be doubled. (Actually, as will be seen,the principle involved is such that the number of movements can betrebled or quadrupled, etc., by appropriate modification, if desired.)

According to this variant, the stop 64F which limits the clockwisemovement of the star piece 38F and gear 37F is replaced by an arm 70F,urged in a counterclockwise direction by a spring 72F. Fixed stop pins74F and 76F limit the arm in each direction of rotation. Anelectromagnet 78F, when energized, moves the arm to the position shownin the drawing.

The arm 70F has a raised surface 80F and a depressed surface 82F.Depending upon whether or not the magnet 78F is energized, the arm 57Fwill strike one surface or the other in its clockwise movement. Thesurfaces are preferably displaced from one another so as to cause thedifference in the resultant angular movement of the star piece and wheel37F to be equal to one-half the displacement between any two adjacentpins such as 41F. By this means, it is possible to arrange the pins toproduce all the even spaces when used in conjunction with the surface F,and all the odd spaces when used in conjunction with the surface 82F.Conversely, the surface 80F may be used in conjunction with the oddspaces, and the surface 82F with the even spaces. It will be understoodthat by suitable arrangement of the parts a damper similar to 56F mayalso be added to the mechanism.

Also, the arm 70F may be provided with more than two stop surfaces, andmechanism may be provided to move the arm to position any desiredsurface in the path of the arm 57F. The described arrangement is adaptedfor use with a simplified control circuit, wherein the magnet 78F isenergized with the magnet for the appropriate pin 41F if said pin is tobe used in conjunction with the stop surface 82F, and is not energizedif said pin is to be used with the stop surface 80F.

A brief review of the operation will now be given. When a lateral motionof the carriage is called for following a photographic exposure, a pin41F is pushed into the path of one of the arms of the star piece,depending on the amount of movement required. The pinion 40F is thenmoved out of mesh (Fig. 4) and the star piece is moved until one of itsarms abuts the pin, the wheel 37F being then locked by the pawl 47F(Fig.

. 5). The wheel 37F and the star piece are then restored to operativeconnection by re-engagement of the pinion 40F (Fig.- 6) and thereafterthe pawl 47F is released (Fig. 7), thereby permitting the wheel to beturned through the precise measured angle. According to the variant ofFig. 9 this angle is determined in part by the surface against which thearm 57F abuts. The motion of the wheel is transmitted through thegearing of Fig. l to turn the shaft 29F through a precise angle, andthis motion is transmitted through the screw 17F to draw the carriage tothe left by an exact amount.

These procedures are repeated for successive characters until after the'entire line is photographed, after which the gears 37F and 19F areunmeshed so that the carriage is restored to its initial position forphotographing a new line, the film then advanced by the sprocket tobring a new line in position.

It will be understood that various modifications of the structure anddetails of design may be carried out without departing from the spiritor scope of the invention. Some of these modifications are describedabove, and others are such as will occur to those skilled in this artupon a reading of this specification.

Having thus described the invention, we claim:

A variable escapement comprising a toothed wheel, an arm pivoted on theaxis of the wheel and having a toothed sector adjacent the wheel, apinion to connect the wheel and sector together, means for disengagingthe pinion from the wheel and sector to allow a movement of the arm, apawl for locking. the wheel during said movement, a plurality ofabutment members, means for placing a selected one of said members inthe path of motion of said arm, a number of spaced stops, means forinterposing one of said stops in the return path of the arm, and meansfor restoring the pinion into engagement with the wheel and sector andfor unlocking the pawl to allow the arm to return to a position againstsaid stop.

